Manage resources on overcommitted KVM hosts

“Summary: A key benefit of virtualization is the ability to
consolidate multiple workloads onto a single computer system. This
consolidation yields savings in power consumption, capital expense,
and administration costs. The degree of savings depends on the
ability to overcommit hardware resources such as memory, CPU
cycles, I/O, and network bandwidth. Technologies such as memory
ballooning and Kernel Same-page Merging (KSM) can improve memory
overcommitment with proper manual tuning. Autonomic reconfiguration
of these controls in response to host and VM conditions can result
in even greater savings. In this article, learn how to apply these
techniques to increase your savings.

“Virtualization promises to increase efficiency by enabling
workload consolidation. Maximizing virtual machine density while
maintaining good performance can be a real challenge:

* A workload’s utilization of resources such as CPU, memory, and
bandwidth for network and storage access varies over time; if you
can dynamically allocate these resources according to demand, then
you can achieve greater density with overcommitment.

* Optimal resource management also depends on factors such as
the system configuration and hardware setup.

“One way to develop a management strategy that incorporates both
factors is to write a set of rules in a policy language. You can
tailor your policy to your unique conditions and effectively
balance your consolidation and performance goals.

“This article explores the challenges associated with aggressive
overcommitment and proposes a policy-driven management tool that
can help you address the challenges. The tool is deployed in a
typical KVM environment and manages two distinct workloads. This
article evaluates the results of this exercise and concludes with
suggestions for additional work items and potential research
topics.”

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